Between December and March, Yota Ito, a 27-year-old member of the Inagawa-kai, allegedly dispatched the girl, 14, from an apartment in Kawasaki City to male customers. Police also arrested a 19-year-old man, a girl, 15, and one other person.
Ito denies the charges, while the other three suspects admit to the charges.
The girl ran away from home in September. In order to prevent the girl from escaping, the suspects were in constant contact and prohibited her from leaving the residence late at night.
According to police, the girl, who lived in a closet in the apartment, served approximately 100 customers for between 15,000 yen and 30,000 yen.
The matter came to light after the girl escaped from the apartment in March.